1. Plasma Poynting-Roberson Effect on Fluffy Dust Aggregate
T. Yamamoto
Inst. Low Temperature Sci.,
Hokkaido Univ.
In collaboration with
T. Minato, H. Kimura (ILTS, Hokkaido U.)
I. Mann, M. Koelher
(Inst. Planetologie, Muenster U.)

2. Dust around Young Main-Sequence Stars & in the Solar System
Observed in debris disk around young MS stars (Vega-like stars) & in the present solar system
Dust disk around βPic
IDP captured in the Earth atmosphere

3. Dust around Young Main-Sequence Stars & in the Solar System
Dust in debris disk around Vega-like stars
Debris after formation of planetary systems?
In situ production by collisions of planetesimals?
Dust in the present solar system
Supply from comets, asteroid collisions & inflow of interstellar dust
Dust must be supplied
because of the limitation of its life time

4. What limits the life time?
Poynting-Roberson effect
Photon PR effect
Absorption and scattering of stellar photons
Plasma PR effect
Collisions of stellar wind ions

5. Forces acting on a dust particle
gravity
PR drag
radiation/wind pressure
star

6. PR drag Drag appears due to aberration on the particle in orbit
Aberration angle

7. Ratio of the plasma and photon PR drags
comparable to photon PR drag for the present solar system
dominant for the young MS stars

8. Momentum transfer cross section
For photons:
Mie theory for spherical particles
DDA, … for aggregates
For charged particles:
Spherical particles
Mukai & Yamamoto 1982, A&A107, 97
Perfect absorption
Minato et al. 2004, A&A, 424, L13
Stopping power is taken into account.
Aggregates: Present study
Any shape & structure
Stopping power

9. Models of dust aggregates
(Mukai et al. 1992, Kimura et al. 2002)
BPCA　(Ballistic Particle-Cluster Aggregations)
Fractal dimension
BCCA (Ballistic Cluster-Cluster Aggregations)
cf. IDP

10. Momentum transfer cross section
Stopping power:
Cross section
: Distribution function of the thickness
: Range of the incident stellar wind ions
Small aggregates:
Large aggregates:
cf. radiation pressure cross section

11. Momentum transfer cross section averaged over the aggregate directions
fluffyness
geometrical cs
penetration

12. Empirical formula aggregate spheroid Momentum transfer cs
Approximated to be
the cross section for
a spheroid of the
same V and S.
aggregate
spheroid

13. Dust around young main-sequence stars
Life time: limited by the photon PR drag
(previous study)
Young MS stars
High mass-loss rate:
Luminosity:
(Wood et al. 2002)
Plasma PR drag will be dominant.

14. Life time against the PR drag
spherical silicate
10 AU to the star
photon
Life time is shorter
for the aggregates
wind plasma

15. Implications
Rate of dust supply should be much larger than the previous estimates
Much larger number of planetesimals in the disk?

16. Mass loss rate vs the age of stars
Wood et al. 2002